849
FXUS65 KTFX 161119
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
419 AM MST MON DEC 16 2024
KEY MESSAGES
- IMPACT SNOW IS EXPECTED STARTING THIS AFTERNOON AND LASTING
THROUGH TUESDAY MORNING.
- STRONG WINDS ARE EXPECTED WEDNESDAY ACROSS THE REGION WITH THE
STRONGEST GUSTS EXPECTED ALONG THE EASTERN SLOPE OF THE
ROCKIES.
- DRIER AND WARMER CONDITIONS ARE EXPECTED BY THE END OF THE
WEEK.
DISCUSSION
- METEOROLOGICAL OVERVIEW:
A WEAK DISTURBANCE WILL BRING A ROUND OF SNOW TO THE AREA STARTING
LATER THIS MORNING AND CONTINUING THROUGH TUESDAY MORNING WITH
THE HEAVIEST AND MOST WIDESPREAD AMOUNTS EXPECTED BETWEEN 4 PM AND
MIDNIGHT TODAY.
A WEAK TROUGH WILL MOVE OVER THE REGION TUESDAY INTO WEDNESDAY
WITH A DISTURBANCE MOVING QUICKLY ACROSS MONTANA AND REACHING THE
DAKOTAS BY THURSDAY. THIS WILL WORK TO BRING A PERIOD OF STRONG
WINDS WITH GENERALLY DRY CONDITIONS EXPECT ALONG THE ROCKIES AND
PORTIONS OF THE HI-LINE EAST OF HAVRE.
BEHIND THIS TROUGH, STRONGER RIDGING STARTS TO BUILD TOWARDS THE
WEEKEND BRINGING A PERIOD OF WELL ABOVE NORMAL TEMPERATURES AND
GENERALLY DRY CONDITIONS. THERE ARE HINTS IN THE MODELS THAT A
PUSH OF PACIFIC MOISTURE COULD BRING SOME PRECIPITATION CHANCES TO
THE AREA BY SUNDAY, HOWEVER UNCERTAINTY IN THE DETAILS STILL
REMAINS HIGH AT THIS TIME.
- FORECAST CONFIDENCE & SCENARIOS:
THERE WAS A MINOR INCREASE IN SNOW TOTALS AT LOWER ELEVATIONS
THROUGH TOMORROW MORNING. THAT BEING SAID, THERE IS SOME DOUBT IN
WHETHER OR NOT THAT INCREASE WILL MATERIALIZE GIVEN HOW WARM
TEMPERATURES ARE EXPECTED TO BE THIS AFTERNOON AND EVENING.
LOOKING AT ALL THE MODEL DATA AND SOUNDINGS, THE MOST LIKELY
SCENARIO AT LOWER ELEVATIONS STILL INVOLVES STARTING OFF AS RAIN
AND SLOWLY TRANSITIONING TO SNOW AFTER SUNSET. THE PROBABILITY
FOR 2 OR MORE INCHES OF SNOW REMAINS LESS THAN 30% ACROSS THE
LOWER ELEVATIONS AND, AS SUCH, NO ADDITIONAL ADVISORIES WILL BE
ISSUED AT THIS TIME.
WHEN LOOKING TOWARDS THE MOUNTAINS, THERE WERE MINIMAL ADJUSTMENTS
TO THE FINAL SNOW TOTALS FOR THIS EVENT COMPARED TO THE PREVIOUS
FORECAST. BUT FOR THE MOST PART MUCH OF THE PREVIOUS MESSAGING
REMAINS THE SAME. THE LATEST PROBABILITIES FOR MORE THAN 6 INCHES
OF SNOW IS AROUND 60% FOR THE TOBACCO ROOT MOUNTAINS AND THE BIG
BELTS AND AROUND 50% FOR THE LITTLE BELTS. AS OF NOW, THE HIGHEST
PROBABILITIES FOR ANYTHING ABOVE 6 INCHES IS CONFINED TO THE
HIGHEST ELEVATIONS AND AWAY FROM WHERE THERE IS A CONCERN FOR
IMPACTS. THUS, THE WINTER WEATHER ADVISORIES REMAIN SUFFICIENT
WITH NO NEED TO UPGRADE AT THIS POINT IN TIME.
LOOKING TOWARDS THE MIDDLE OF THE WEEK, THERE IS A CONCERN FOR
STRONG WINDS WEDNESDAY INTO EARLY THURSDAY MORNING. THE MAIN
DEBATE AND UNCERTAINTY IS WHETHER OR NOT STRONG WINDS WILL TURN
INTO HIGH WINDS. THERE IS A DISCONNECT IN THE MODELS ON TIMING
WHICH COULD MAKE OR BREAK THE POTENTIAL FOR THIS EVENT. IF THE
DISTURBANCE ARRIVES EARLIER IN THE DAY THEN THE STRONGER WINDS
HAVE A BETTER CHANCE AT MIXING DOWN TO THE SURFACE. ADDITIONALLY,
IF A MOUNTAIN WAVE DEVELOPS THIS WILL ALSO WORK TO ENHANCE THE
PROCESS AND MAKE HIGH WINDS MORE LIKELY. BUT SHOULD THE
DISTURBANCE ARRIVE LATER IN THE DAY, ESPECIALLY AFTER THE DIURNAL
INVERSION STARTS TO SET UP, IT BECOMES INCREASINGLY LIKELY THAT
THE STRONGEST WINDS WILL STAY ALOFT WITH NO IMPACT TO THE SURFACE.
AND IT IS CRUCIAL TO NOTE THAT WEDNESDAY WILL BE A WINDY DAY. THE
PROBABILITIES OF GUSTS OVER 30 MPH IS ABOVE 70% FOR MUCH OF THE
CWA. BUT BECAUSE THERE ARE UNCERTAINTIES IN HIGHER WINDS REACHING
THE SURFACE, A HIGH WIND WATCH WILL NOT BE ISSUED AT THIS TIME.
SHOULD THE MODELS COME INTO BETTER AGREEMENT DOWN THE ROAD, IT IS
VERY POSSIBLE THAT A HEADLINE MAY BE NEEDED WITH FUTURE UPDATES.
-THOR
AVIATION
16/06Z TAF PERIOD
A FEW SNOW SHOWERS LINGER ACROSS THE SW MT MOUNTAINS THIS EVENING
WITH LOCAL MOUNTAIN OBSCURATION PERHAPS SOME VERY BRIEF VIS/CIG
REDUCTIONS AT KEKS BUT OTHERWISE CLOUDS DECREASE THROUGH TONIGHT
WITH VFR CONDITIONS PREVAILING AT MOST TERMINALS THROUGH MONDAY
MORNING. A FRONTAL BOUNDARY MOVING SOUTH FROM AB WILL SHIFT WINDS
TO THE NW AT KCTB AND KHVR LATER TONIGHT WITH SOME POTENTIAL FOR
LOW CLOUDS MOVING INTO THESE TERMINALS FOLLOWING THE FRONTAL
PASSAGE. HI-RESOLUTION MODEL GUIDANCE HAS 30-50% CHANCE FOR
CEILINGS LESS THAN 3000FT AT KHVR BUT LESS THAN 30% CHANCE FOR
KCTB. CLOUDS INCREASE AGAIN ON MONDAY AS THE NEXT WEATHER SYSTEM
MOVES IN FROM THE WEST WITH LIGHT SNOW DEVELOPING FROM SOUTH TO
NORTH ACROSS THE AREA MONDAY AFTERNOON THROUGH MONDAY EVENING.
HOENISCH
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 36 20 29 16 / 20 60 20 20
CTB 30 13 21 8 / 10 60 10 30
HLN 34 23 37 26 / 60 60 20 20
BZN 34 20 37 22 / 60 70 30 10
WYS 26 15 30 18 / 90 90 70 40
DLN 33 20 38 24 / 50 30 10 10
HVR 28 13 21 5 / 0 50 30 40
LWT 34 20 31 16 / 10 70 30 30
TFX WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY FROM 2 PM THIS AFTERNOON TO 9 AM MST
TUESDAY FOR BIG BELT, BRIDGER AND CASTLE MOUNTAINS-EAST GLACIER
PARK REGION-GALLATIN AND MADISON COUNTY MOUNTAINS AND CENTENNIAL
MOUNTAINS-LITTLE BELT AND HIGHWOOD MOUNTAINS.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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